Friction pad containing high temperature stable continuous filament glass fibers

ABSTRACT

Composition and process for the preparation of high temperature stable continuous glass fibers with an upper temperature use limit of 2300 DEG  F. are provided. The compositional formulation, in mole percent, is 62-85% SiO2, 10-20% Al2O3, 5-15% MgO, 0.5-5% TiOx, and 0-5% ZrO2. The continuous fibers are prepared by an economical direct melt method, and demonstrate high tensile strength, high Young&#39;s modulus, and low linear thermal shrinkage characteristics. Friction pads containing these high temperature stable continuous glass fibers are also provided.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 08/575,060 filed Dec. 12, 1995, now U.S. Pat. No. 5,585,312, which is a continuation of U.S. patent application Ser. No. 294,258 filed Aug. 23, 1994, now abandoned.

FIELD OF THE INVENTION

The present invention relates to continuous filament glass fibers and friction pads containing the same. More particularly, it relates to a relatively low cost method of producing continuous filament glass fibers with an upper temperature use limit equivalent to refractory ceramic fiber of 2300° F. Specifically, the invention relates to continuous filament glass fibers which may be used as a reinforcement material in friction and polymer reinforcement applications. For example, the continuous filament glass fibers may be used for reinforcement of organic matrix material for a wide variety of applications, including for use in products such as friction pads.

BACKGROUND OF THE INVENTION

Glass fibers are the oldest type of strong fibers used in applications such as composite structural materials. Although the possibility of forming fibers from heat-softened glass was known thousands of years ago, these fibers were discontinous, and it was not until the 1930's that the production of continuous glass fiber became commercially viable. The first use for substantial quantities of continuous glass fiber was for electrical insulation of fine wires used at elevated temperatures. The continuous glass fibers for this application became known as "E" glass because of their electrical properties. "E" glass does not have a specifically defined composition, but is a type of glass of defined electrical properties, and is generally a low alkali, calcium aluminum borosilicate. "E" glass has an upper temperature use limit of about 1100° F.

Improvements over the properties of "E" glass have been made through elimination of the alkali and other low melting components. This resulted in the development of "S" glass, known for its strength properties. "S" glass is a magnesium-aluminosilicate composition with considerably higher strength and modulus, and an upper temperature use limit of about 1500° F.

The preparation of glass fiber with higher temperature use limits is desirable, and has been pursued through post treatment of "S" glass. U.S. Pat. No. 3,402,055 describes the application of a variety of substances through aqueous or organic solvent base treatments of magnesium-aluminosilicate fibers to enhance temperature resistance of the fibers. U.S. Pat. No. 4,379,111 describes uniformly coating fibers with chromium oxide to enhance heat resistance over uncoated fibers or non-uniformly coated fibers of the same composition. U.S. Pat. No. 4,492,722 describes the deposition of a surface coating consisting essentially of TiO₂ from an organic solution to extend the upper use temperature limit to approximately 2000° F. These post treatments, however, are expensive processes.

Traditional refractory ceramic fiber (RCF) has an upper temperature use limit of 2300° F. and is inexpensively produced in several forms, but all of these forms are discontinuous. Continuous filament ceramic fibers are known, but they must be produced through expensive sol-gel routes.

There are many advantages of fiber in continuous form over traditional discontinuous refractory ceramic fiber, including the elimination of shot, the ability to chop filaments to any desired length, the ability to utilize the filaments directly for the manufacture of textile products, product performance characteristics, and the ability to custom manufacture fibers of known diameter.

Shot refers to high density, unfiberized particles which are detrimental to thermal efficiency, act as stress risers in reinforcing applications, and cause excessive wear in friction applications.

The ability to chop continuous filaments to any desired length is particularly advantageous in papermaking and in reinforcing applications.

The ability to utilize continuous filaments directly for spinning and weaving for the manufacture of textile products eliminates the cost associated with the organic carriers required with traditional refractory ceramic fibers. Textile products produced with traditional discontinuous refractory ceramic fibers typically have lower tensile strength when compared to products produced with continuous fibers. The continuous filaments can be woven into cloth for fire protection or other high temperature applications.

Since continuous fiber can be manufactured more reproducibly than discontinuous fiber, the custom manufacture of fibers of known diameter, within narrow tolerances, is more facile using fibers in continuous form. In addition, the ability to control fiber diameter, especially the control of fiber diameters to values greater than those considered respirable, is beneficial from the aspect of physiological considerations as well as for thermal and reinforcement performance.

The use of high temperature continuous filament glass fiber in friction applications is seen as being particularly desirable. Heretofore, discontinuous refractory ceramic fibers have been used to reinforce the matrix material utilized in friction pads as well as comparable glass fibers such as rockwool, "E" glass, and "S" glass. A common drawback of each of these prior art glass fibers, however, is the fact that they are well known to fade or lose further strength, especially at higher temperatures and in hard braking applications.

Thus, the need exists for a friction pad containing continuous filament glass fibers which will not degrade readily under severe braking conditions.

SUMMARY OF THE INVENTION

An object of the present invention is to prepare continuous filament glass fibers which have an upper temperature use limit higher than that of "S" glass.

Another object of the present invention is to prepare high temperature stable continuous filament glass fibers by a direct melt method which is more economical than sol-gel methods or post treatment processes.

A further object of the present invention is to prepare continuous filament glass fibers with an upper temperature use limit equivalent to refractory ceramic fiber.

Still another object of the present invention is to prepare friction pads containing the continuous filament glass fibers, as above.

These and other objects and advantages of the invention set forth herein are accomplished by the present invention as hereinafter described and claimed.

We have found that continuous filament glass fibers with strength and thermal stability equivalent to traditional refractory ceramic fibers can be produced by conventional melt drawing techniques in the following compositional ranges expressed in mole percent:

    ______________________________________                                         SiO.sub.2       62-85,                                                         Al.sub.2 O.sub.3                                                                               9.5-20,                                                        MgO             5-15.5,                                                        TiO.sub.x       0.5-5, (wherein 0 ≦ x ≦ 2),                      ZrO.sub.2       0-5.                                                           ______________________________________                                    

The present invention therefore provides high temperature stable glass fibers consisting essentially of about 62 to about 85 mole percent SiO₂, about 9.5 to about 20 mole percent Al₂ O₃, about 5 to about 15.5 mole percent MgO, about 0.5 to about 5 mole percent TiO_(x), wherein 0≦x≦2, and 0 to about 5 mole percent ZrO₂.

The present invention further provides high temperature stable continuous filament glass ceramic fibers comprising about 62 to about 85 mole percent SiO₂, about 9.5 to about 20 mole percent Al₂ O₃, about 5 to about 15.5 mole percent MgO, about 0.5 to about 5 mole percent TiO_(x), wherein 0≦x≦2, and 0 to about 5 mole percent ZrO₂.

We have also found that continuous filament fibers with preferred compositions within the above range have physical properties and thermal performance better than traditional refractory ceramic fibers. In particular embodiments of the invention, we have observed that the use of TiO₂ at low percentages in a preferred range of about 1 mole % to about 2 mole % results particularly in an increase in the upper use temperature limit of produced fibers, namely in beneficial low shrinkage characteristics for the produced fibers.

The present invention provides a process for the production of high temperature stable glass fibers, comprising melting a ceramic powder feed to form a melt, and forming said melt into filaments, wherein said ceramic powder feed consists essentially of about 62 to about 85 mole percent SiO₂, about 9.5 to about 20 mole percent Al₂ O₃, about 5 to about 15.5 mole percent MgO, about 0.5 to about 5 mole percent TiO_(x), wherein 0≦x≦2, and 0 to about 5 mole percent ZrO₂.

The present invention also provides, by virtue of the low shrinkage characteristics and increased fiber diameters of produced filaments having compositions in the range specified above, useful compositions for the manufacture of refractory ceramic fibers by traditional blowing or spinning methods.

The present invention provides a process for producing continuous filament glass fibers, with an upper use temperature limit equivalent to refractory ceramic fiber of 2300° F. by an economical direct melt method.

The present invention therefore provides a process for the production of high temperature stable continuous filament glass fibers, comprising melting a ceramic powder feed to form a melt, and drawing said melt into continuous filaments, wherein said ceramic powder feed comprises about 62 to about 85 mole percent SiO₂, about 9.5 to about 20 mole percent Al₂ O₃, about 5 to about 15.5 mole percent MgO, about 0.5 to about 5 mole percent TiO_(x), wherein 0≦x≦, and 0 to about 5 mole percent ZrO₂.

The present invention further provides continuous filament glass fibers with increased upper use temperature limits, for use as insulation materials in a variety of forms, including woven textile products, ropes, braids, boards, papers, blankets, and mats.

The present invention also provides continuous filament glass fibers with increased upper use temperature limits and improved physical properties, for reinforcement of organic matrix materials, to provide increased tensile strength and modulus, increased flexural strength and modulus, and increased deflection temperature under load.

The present invention further provides continuous filament glass fibers with increased upper use temperature limits for use in friction materials; such as phenolics or for reinforcement of matrices of carbonized carbonaceous binders, otherwise known as carbon bodies, for such applications as friction discs or friction pads for use in disc brakes or drum brakes, ranging from light automotive to severe duty applications.

The present invention further provides a friction pad comprising a reinforced organic matrix material, wherein the matrix is reinforced with at least one reinforcement material, said at least one reinforcement material including high temperature stable glass fibers consisting essentially of about 67.5 to about 85 mole percent SiO₂, about 9.5 to about 20 mole percent Al₂ O₃, about 5 to about 15.5 mole percent MgO, about 0.5 to about 5 mole percent TiO_(x), wherein 0≦x≦, and 0 to about 5 mole percent ZrO₂.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a molar composition diagram of glass components.

FIG. 2 is a block flow diagram of continuous filament production.

FIG. 3 is a graphical representation of fiber tensile strength versus temperature.

FIG. 4 is a graphical representation of the Youngs' Modulus of fiber versus temperature.

FIG. 5 is a graphical representation of stress versus displacement based upon a Three Point Bend Test.

FIG. 6 is a graphical comparison of flex strength and displacement to 850 psi of glass fibers of the present invention with prior art glass fibers.

FIG. 7 is a graphical comparison of flex displacement to fracture at room temperature and flex displacement to 860 psi at room temperature of glass fibers of the present invention with prior art glass fibers.

FIGS. 8A-8D are plurality of graphical representations relating to a series of friction tests performed on friction pads containing 1/4 inch "S" glass fibers.

FIGS. 9A-9D are plurality of graphical representations relating to a series of friction tests performed on friction pads containing 1/4 inch "E" glass fibers.

FIGS. 10A-10D are plurality of graphical representations relating to a series of friction tests performed on friction pads containing the high temperature glass fibers of the present invention.

FIGS. 11A-11D are plurality of graphical representations relating to a series of friction tests performed on friction pads containing standard refractory ceramic fibers.

FIGS. 12A-12D are plurality of graphical representations relating to a series of friction tests performed on friction pads containing another type of standard refractory ceramic fibers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to the preparation of improved glass fibers for applications which include insulation and reinforcement of various matrices, the improvement comprising increased strength properties, improved shrinkage characteristics, and the preparation of these glass fibers with an upper use temperature limit equivalent to refractory ceramic fiber of 2300° F. but in a continuous form, through an economical direct melt method.

The objects of the invention are accomplished through the use of specific ranges of inorganic components in the preparation of glass fiber compositions. In particular, we have found that continuous filament glass fibers with strength and thermal stability equal to traditional refractory ceramic fibers can be produced from the following inorganic compounds in the composition ranges expressed in mole percent:

    ______________________________________                                         SiO.sub.2                                                                               about        62-85,                                                   Al.sub.2 O.sub.3                                                                        about        9.5-20,                                                  MgO      about        5-15.5,                                                  TiO.sub.x                                                                               about        0.5-5 (wherein 0 ≦ x ≦ 2),                 ZrO.sub.2                                                                               about        0-5.                                                     ______________________________________                                    

The inorganic feed compounds are commercially available in reagent and technical grade, for example silica, high quality calcined alumina, magnesia and rutile titania, from a number of domestic supplies.

The continuous filament glass fibers prepared using inorganic compounds in the above composition ranges can be produced by conventional melt drawing techniques.

We have also found that continuous filament fibers with preferred compositions within the above range have physical properties such as tensile strength, Young 's modulus, and thermal shrinkage performance, such as exhibited in testing at 2300° C. for 24 hours, which are improved over traditional refractory ceramic fibers. In particular, we have found that the incorporation into the fiber of TiO_(x), such as TiO₂, at preferred low percentages of about 1 mole % to about 2 mole %, and most preferably 1.25 mole % to about 1.5 mole % provides an increase in the upper use temperature limit of produced fibers, namely in beneficial low shrinkage characteristics for the produced fibers.

FIG. 1 is a molar composition diagram of glass components SiO₂, Al₂ O₃ and MgO projected on a 0% titania plane. FIG. 1 details drawable glass fiber compositions in the lightly shaded area, and preferred drawable compositions containing 1.5% titania which particularly yield target properties in terms of improved strength and improved shrinkage characteristics in the dark shaded area. For the continuous filament glass fibers of the present invention, target properties with regard to improved strength are generally defined as tensile strength greater than about 250 Ksi and Young's modulus greater than about 12 Msi. The target property with regard to improved shrinkage characteristics is generally defined as less than about 3% shrinkage at 2300° F. for 24 hours. The lightly shaded area of FIG. I which lies within the compositional ranges of the glass ceramic components detailed above generally corresponds to the preferred ranges of those components, and the dark shaded area of FIG. 1 generally corresponds to the most preferred ranges of those components.

Compositions of high temperature stable continuous filament glass fibers of the present invention comprise

i) about 62 to 85 mole % SiO₂, preferably about 68 to 82% SiO₂, most preferably about 72 to 80% SiO₂ ;

ii) about 9.5 to 20 mole % Al₂ O₃, preferably about 10 to 16% Al₂ O₃, most preferably about 10 to 16% Al₂ O₃ ;

iii) about 5 to 15.5 mole % MgO, preferably about 6 to 14% MgO, most preferably about 7 to 14% MgO;

iv) about 0.5 to 5 mole % TiO_(x), preferably about 1 to 2% TiO_(x), most preferably about 1.25 to 1.5% TiO_(x) ; and

v) 0 to about 5 mole % ZrO₂, preferably 0 to about 3% ZrO₂, most preferably about 0 to 2% ZrO₂. In some embodiments, ZrO₂ has been found useful in obtaining high tensile strength.

While the above compositions are preferred for continuous filament glass fibers, such compositions display improved properties when utilized in discontinuous high temperature stable glass fibers, also.

The present invention provides a method of producing continuous filament glass fibers, with an upper use temperature limit equivalent to refractory ceramic fiber of 2300° F. by an economical direct melt method. FIG. 2 is a block flow diagram of continuous filament production. The major steps in continuous filament production include preparation of a ceramic powder feed, introduction of the powder feed into a melt furnace, melt conditioning (such as fining) and delivery to the fiber-drawing furnaces, called bushings, from which the filaments are drawn, followed by sizing and winding of the fibers.

The manufacture of glass fiber products is generally considered to comprise three stages. The major steps illustrated in FIG. 2 describe Stages 1 and 2. Stage 1 consists of the actual glass manufacture, the fusion of selected raw materials in a melt furnace and delivery to the fiber-drawing furnaces. Stage 2 consists of the conversion of the glass into fibers in the fiber-drawing furnace, called the bushing. Continuous glass fibers are prepared through the rapid mechanical attenuation of molten drops of glass exuding from a large number of nozzles, usually about 200, located on the underside of the bushing which is usually electrically heated. Molten glass exudes from each nozzle where the glass forms a meniscus during fiber-drawing as a result of the mechanical attenuation. The individual fibers, known as filaments, pass over an applicator which deposits a protecting and lubricating size onto the filaments before they are gathered into bundles of filaments called strands. The strands then pass through a light water spray on their way to the winder, which consists of a slightly expandable rotating cylinder, called a collet, covered during the winding process by a removable plastic or paper tube onto which the strand is wound, and a device which lays successive lengths of strands onto the tube at small angles to one another to facilitate subsequent unwinding. Stage 3 consists of the conversion of the glass fibers into products.

Compositions of the present invention have melting points and drawing temperatures between about 1500° C. and about 2000° C. depending upon the specific component ranges utilized. Since the melting points and drawing temperatures are in excess of 1500° C. high temperature melting and drawing equipment are utilized in the manufacture of filaments according to the present invention. Other than the use of high temperature materials of construction, the actual melting and drawing of the filaments by the method of the present invention is accomplished following techniques known to those skilled in the art for melting and drawing of conventional fiberglass.

Although conventional direct melt methods are preferred due to economy of production, compositions of the present invention demonstrate improved properties over traditional refractory ceramic fibers, when manufactured as continuous refractory ceramic fibers by sol-gel methods, as well as refractory ceramic fibers manufactured by traditional blowing or spinning methods, or any other method known to those skilled in the art. Manufacture of high temperature stable continuous glass filaments according to the present invention results in increased fiber diameter, relative to standard aluminosilicate materials, when produced using a blowing fiberization technique. The ability to control fiber diameter, especially the ability to control fiber diameters to larger values, is beneficial from the aspect of physiological concerns as well as for certain thermal and reinforcement performance.

Compositions of the present invention demonstrate, within a preferred range of about 1 mole % to about 2 mole % TiO₂ in the overall composition and a most preferred range of about 1.25 to about 1.5 mole % TiO₂, a beneficial effect of low shrinkage characteristics for produced filaments. The reason for the improvement in shrinkage characteristics is not completely understood. While not being bound by theory, it is believed that the decreased shrinkage is due to a change in micro-structure within the fiber, from an essentially amorphous structure to a nucleated structure which readily crystallizes when reheated. This theory, however, has not been confirmed by detailed analysis.

We have found that the desired properties of the continuous filament glass fibers of the present invention can be enhanced when at least a portion of the titanium utilized in the melt is in a reduced form as compared to TiO₂. This can be accomplished by a variety of methods. One method is to utilize a form of titanium oxide other than, or in addition to, an appropriate portion of titanium dioxide (+4 oxidation state) in the melt. Such other forms include TiO (+2 oxidation state) and Ti₂ O₃ (+3 oxidation state). Another method is to introduce at least a portion of the titanium component into the melt in the form of metallic titanium. A further method is to add other reducing agents into the melt (or furnace), such as carbon or carbon monoxide, or to use a furnace with a reducing environment, such as a graphite furnace.

The high temperature stable continuous filament glass fibers of the present invention demonstrate many advantages over traditional refractory ceramic fiber in discontinuous form. These advantages include, but are not limited to, the elimination of shot, the ability to chop filaments to any desired length(s), the ability to utilize the filaments directly for the manufacture of textile products, and the ability to custom manufacture fibers of known diameter.

Shot refers to high density, unfiberized particles which are detrimental to thermal efficiency, act as stress risers in reinforcing applications, and cause excessive wear in friction applications. The elimination of shot in the production of the continuous filament glass fibers of the present invention eliminates the necessity of an additional beneficiation step which is often employed in the production of other types of glass fibers in order to remove the deleterious shot from the fibers.

The ability to chop continuous filaments to any desired length is particularly advantageous in papermaking and in reinforcing applications where the performance of the end product is dependent upon the length of the fibers employed in the application as well as on the distribution of the lengths of those fibers. By chopping continuous fibers to preselected length(s), a narrower distribution of fiber lengths is obtained than is otherwise possible using discontinuous fibers.

Since continuous fiber can be manufactured more reproducibly than discontinuous fiber, the custom manufacture of fibers of known diameter, within narrow tolerances, is more facile when producing fibers in continuous form. By controlling fiber diameter, especially the control of fiber diameters to achieve larger values, fibers may be easily produced to match specifications of end-use applications in order to maximize beneficial thermal and reinforcement performance. Higher reproducibility for the production of fibers of this invention will result in a narrower distribution of diameters for produced fibers with concomitant improved performance in targeted applications. The average diameter of fibers produced according to the present invention are controllable within a range of about 5 to about 50 microns, and are preferably used in the range of about 5 to about 25 microns.

The continuous filament glass fibers of the present invention demonstrate an upper temperature use limit significantly higher than that of "E" glass or "S" glass. The continuous fibers of the present invention, therefore, are suitable for applications which currently use "E" glass or "S" glass while offering greatly improved high temperature stability in those applications.

The present invention demonstrates the preparation of continuous filament glass fibers with an upper temperature use limit equivalent to refractory ceramic fiber of 2300° F. while utilizing a direct melt method which is more economical than sol-gel methods or post treatment processes. The continuous fibers of the present invention, therefore, are suitable for applications which currently use traditional refractory ceramic fibers, while offering the improvements attributable to the continuous nature of the fiber and improved economy in those applications, as well as improved physical properties described above.

The continuous filament glass fibers of the present invention demonstrate high upper use temperature limits and are suitable for use by methods known in the art as insulation materials in a variety of forms, including woven textile products, ropes, braids, boards, papers, blankets, and mats. The ability to utilize the continuous filaments of the present invention directly for such processes as weaving and spinning for the manufacture of textile products provides a distinct advantage over the prior art, by eliminating the organic carriers required with traditional refractory ceramic fiber.

The high temperature stable continuous filament glass fibers of the present invention are suitable for use in the reinforcement of organic matrix materials. Reinforcement of organic matrices by the fibers of the present invention provide improved properties, including increased tensile strength and modulus, increased flexural strength and modulus, and increased deflection temperature under load. Organic matrices containing continuous fiber reinforcement display exceptional mechanical properties and are generally termed advanced composites to distinguish them from chopped-fiber reinforced materials.

Suitable organic materials for use as matrices in composites reinforced by the fibers of the present invention are generally polymeric materials of two broad classifications, thermoplastics and thermosets. Thermoplastics are polymeric materials which reversibly pass into a plastic state when heated and into a hardened state when cooled. Thermosets are polymeric materials which pass once through a plastic state and then harden irreversibly due to the formation of crosslinks.

Examples of thermoplastic polymers suitable for use in fiber-reinforced composite materials include, but are not limited to, polyamides such as nylon-6,6 and nylon-6, polyolefins such as polyethylene and polypropylene, polycarbonates, polyacetals, polystyrene, polysulfones, polyphenylene sulfide, and essentially linear polyesters and polyurethanes.

Examples of thermoset polymers suitable for use in fiber-reinforced composite materials include, but are not limited to, alkyd resins, diallyl ortho-phthalate resins, epoxy resins, phenolic resins, melamine resins, urea resins, silicone resins, polyester resins, and urethane resins.

The high temperature stable continuous filament glass fibers of the present invention are suitable for use in the reinforcement of matrices of carbonized carbonaceous binders, otherwise known as carbon bodies, produced conventionally. These carbon bodies are useful for a wide variety of applications, wherever strong lightweight bodies are needed, and are especially useful in friction applications. One such application is as friction pads for use in brakes, and particularly as friction pads for use in disc brakes, by virtue of the high heat capacity, high strength, high temperature stability, and high coefficient of friction of the glass fiber-reinforced carbon bodies. The continuous nature of the high temperature glass fibers of the present invention allows them to be successively circumferentially wound, axially compressed, and radially overlapped in order to prevent failure mechanisms due to improper orientation of the reinforcing fibers.

The continuous filament glass fibers of the present invention are useful for other friction applications, ranging from automotive to severe duty, when used with conventional binders such as phenolics, fillers, and friction modifiers, if any.

Loading levels of the high temperature stable glass fiber of the present invention in a matrix material may range from about 1% to about 50% by weight, more preferably, from about 2% to about 30% by weight, and even more preferably, from about 5% to about 20% by weight. It will also be appreciated that the high temperature stable glass fiber may be employed with other glass fibers such as "E" glass to give the matrix material additional strength at certain service temperatures.

The high temperature glass fibers of the present invention have been found to have particular application in friction pads. That is, friction pads made from a reinforced matrix material which has been reinforced with reinforcement material containing the continuous filament glass fibers of the present invention have been found to exhibit improved flexural strength and improved displacement as compared to friction pads containing "S" glass or "E" glass reinforcement. The matrix materials reinforced with the glass fibers of the present invention which form the friction pads have been found to be very strong, very tough composites, exhibiting flexural strength which is twice as high as composites using "E" glass or rockwool. Without being limited to theory, we believe that this result is a function of the improved modulus of the glass fibers of the present invention as compared to "E" glass.

In brakes, these characteristics permit increased freedom in formulating brake composites by allowing a reduction of certain expensive components. It is believed that brake pads or discs using these composites will reduce wear on the rotors. Furthermore, the increased flexibility of the composites should reduce brake pad noise.

To evidence the superior properties of the glass fibers of the present invention over conventional glass fibers such as rockwool, "E" glass and "S" glass, several tests comparisons were made. It will be appreciated that, in order to test the fibers, friction pads were prepared as is well known in the art using typical and conventional materials, except that the type of fiber employed was changed for each brake formulation. One preferred example of a typical brake formulation is provided hereinbelow, but it will be understood that the present invention is not to be limited thereto. Phenolic binders were used in conjunction with these standard brake formulations.

Also, the composition of the fiber of the present invention for these tests fall within the ranges specified hereinabove and specifically include the following: about 72 mole % SiO₂, about 13 mole % Al₂ O₃, about 13.5 mole % MgO, and about 1.5 mole % TiO₂. The fibers were substantially uniform 1/4 inch, chopped fibers in hard bundles, and 8 microns in diameter. "Hard bundle" refers to the sizing used to hold the bundle of fibers together. Those that are designed to maintain their integrity after chopping are considered "hard", while those designed to fall apart after chopping are considered "loose".

Preferred lengths for the chopped fibers of the present invention range from about 1/16 of an inch to about 3/4 of an inch, with about 1/16-inch to about 1/4-inch being most preferred.

Turning to the FIG. 5, this FIG. depicts the results of a three point bend test comparison among four brake pad formulations, including a formulation containing the fibers of the present invention. This three point bend test, which is well known in the friction industry and can be performed by those skilled in the art without undue experimentation, generally takes a predetermined, elongated segment of the brake composite and places it onto a test apparatus which pushes on one side at a point in the middle of the elongated segment while holding the other side at points on the segment's ends. In FIG. 5, the amount of applied stress (in psi) or Modulus of Rupture (MOR) is graphed versus displacement (in inches). Displacement identifies the amount of bend of the segment before rupture. As shown, the segment of the brake composite containing the chopped, continuous fibers of the present invention (e.g., 1/4" hard bundle continuous filament) was able to handle significantly more applied stress and exhibited a significant increase in displacement as compared to 1/4" and 1/8" "E" glass, rockwool, and even "E" glass formulations having three times higher "E" glass loadings in the segment.

FIG. 6 is another comparison among various friction pad formulations, including a formulation containing the fibers of the present invention, denoted as "CRF" in the FIG. The graph in this FIG. compares flexural strength in psi, denoted as "Series 1" in the graph, and displacement (in inches) to 850 psi, denoted as "Series 2" in the graph.

With regard to flexural strength, it will be appreciated that the friction composite containing matrix material reinforced with the fibers of the present invention (CRF) showed significant improvement in flex strength over each of the other friction composites using different reinforcement materials, such as rockwool or "E" glass, even when these composites were loaded at two or three times higher levels of the particular reinforcement material. The friction composite utilizing the continuous fibers of the present invention exhibited a flexural strength of almost 8000 psi, whereas the next closest composite, one having a three times higher "E" glass loading, exhibited a flexural strength of only about 5000 psi. Thus, the glass fibers of the present invention appear to be effective in providing reinforcement to matrix material in friction pads and exhibiting flexural strength of well over 5000 psi, and even above 7000 psi.

As for flex displacement to 850 psi, it will be appreciated that the friction composite containing matrix material reinforced with the glass fibers of the present invention (CRF) showed significant improvement in that characteristic as well. Displacement was increased significantly to over 0.16 inches as compared to the composites utilizing fibers of the prior art which exhibited displacements of less than 0.10 in most instances. Thus, the glass fibers of the present invention appear to be effective in providing reinforcement to matrix material in friction pads and increasing displacement to well over 0.10 inches, and even above 0.14 inches at 850 psi.

FIG. 7 shows still another comparison among various friction pad formulations, including a formulation containing the continuous fibers of the present invention, denoted as "CRF" in the FIG. This FIG. compares displacement (in inches) of the friction composites to fracture when flexed at room temperature and displacement (in inches) of the composites to 860 psi when flexed at room temperature, the composites being molded at 6000 pal. Specifically, the reinforcement materials used included rockwool, "E" glass and the fiber of the present invention. 1/4 inch and 1/8 inch chopped "E" glass fibers used with phenolic binder was used as the baseline formulation.

It will be appreciated that the friction composite containing matrix material reinforced with the glass fibers of the present invention (CRF) showed a significant increase in displacement to fracture and displacement to 860 psi as compared to friction composites containing matrix material reinforced with other fibers, even those having two to three times higher loadings. Displacement to fracture of CRF was over 0.04 inches as compared to the other fibers where displacement to fracture was closer to about 0.02 inches. Displacement to 860 psi was increased significantly to over 0.18 inches as compared to the composites utilizing fibers of the prior art which exhibited displacements of less than 0.1 in most instances. Thus, the continuous fibers of the present invention appear to be effective in providing reinforcement to matrix material in friction pads and increasing displacement to well over 0.10 inches, and even above 0.18 inches at 860 psi.

FIGS. 8A-8D to 12A-12D compare a series of friction tests performed on friction pads made from matrix material reinforced with various glass and ceramic fibers. Specifically, the friction pad/brake formulations included the following material at the following load levels.

    ______________________________________                                         Material             Loading Level (Wt. %)                                     ______________________________________                                         Calcuim Carbonate    40.6                                                      Barium Sulfate       15.2                                                      Phenolic Resin (Cardolite NC-126)                                                                   15.2                                                      Cashew Particle (10A40)                                                                             15.2                                                      Aromatic Polyamide Fiber (Kevlar ®)                                                             3.8                                                       Fiber                10.0                                                      ______________________________________                                    

FIG. 8A-8D are uses a friction pad containing 1/4 inch "S" glass fibers; FIG. 9 use a friction pad containing 1/4 inch "E" glass; FIGS. 10A-10D use a friction pad containing the glass fiber of the present invention; FIG. 11A-11D use a friction pad containing a standard ceramic fiber used in passenger car and light truck disc brake pads; and FIG. 12A-11D use a friction pad containing another type of ceramic fiber typically used for super heavy duty brakes on heavy trucks and the like. The tests were performed on a conventional automotive dynamometer in accordance with Procedure A04F, a well known, documented procedure commonly used in the friction industry for determining various friction characteristics, including pad and rotor wear, brake effectiveness, and fade properties.

With regard to FIGS. 8A to 12A, the graphs in the upper right-hand corner of the FIGS. relate to initial wear characteristics in "breaking the brake in," and allows each friction pad to perform under optimal conditions.

The graphs in FIGS. 8B to 12B and 8C to 12C These two very important graphs depict the effectiveness of braking at 30 mph (FIGS. 8B to 12B) and 60 mph (FIGS. 8C to 12C), and, specifically, indicate how much pressure must be applied in a brake line to the friction pad in order to provide a particular deceleration rate. The test is run in four stages or efforts, with each friction pad undergoing a predetermined series of extensive steps designed to "age" the friction pad between efforts. Once the friction pad has been properly "aged", the effectiveness is then tested again and so on. A friction pad is considered effective if it does not degrade with each effort. That is, the line pressure used to reach a particular deceleration rate should preferably remain essentially constant. It will be appreciated that when this happens, each of the lines on the graph will be very close together or essentially be the same. On the other hand, if the lines are spread out, it means the friction pad is degrading as it is "aged," and it will take more pressure to get the same deceleration rate.

Upon viewing and comparing the graphs in FIGS. 8B to 12B and 8C to 12C) it will be appreciated that friction pads employing ceramic (FIGS. 11A-11D to 12A-12D fibers as well as the glass fibers of the present invention (FIGS. 10A-10D) are the most effective in braking. In contrast, the friction pads employing the "S" glass (FIGS. 8A-8D) and "E" glass (FIGS. 9A-9D) fibers exhibited a tendency to degrade more rapidly.

The graphs in FIGS. 8D to 12D show fade and recovery properties. To perform this test, the rotor temperature of the brake is increased over a series of braking applications. Upon each application, the amount of applied pressure required to stop is measured. It will be appreciated that, as the temperature increased, the amount of applied pressure also increases. Also, as the temperature increases, the differential between the maximum pressure and minimum pressure also increases.

In the recovery portion of the graph, the temperature is lower or returned to normal over another series of braking applications. Desirably, the pressure applied to the brakes should return back to where it originally started as quickly as possible.

Upon review of the FIGS. 8A-8D to 12A-12D it will be appreciated that the friction pad utilizing the continuous filament glass fibers of the present invention (FIGS. 10A-10D exhibited excellent fade and recovery properties which exceeded the fade and recovery properties of the "S" glass and "E" glass fibers (FIGS. 8A-8D to 9A-9D) and which were as good as, if not better than, the fade and recovery properties of the refractory ceramic fibers (FIGS. 11A-11D to 12A-12D).

Thus, it will be appreciated that the high temperature stable glass fibers of the present invention are effective in reinforcing organic and/or carbon matrix material used in friction pads. The fibers are the present invention are particularly suitable for disc brake disc pads for passenger cars and light trucks, but are not necessarily limited thereto, the fibers also being useful in other friction pad applications, including but not limited to clutch friction pads, heavy duty truck brake blocks, and brake shoes for drum brakes.

The specific embodiments described below are intended to illustrate, but not to limit, the present invention.

SPECIFIC EMBODIMENTS OF THE INVENTION

Continuous filament glass fibers were prepared according to the general procedure detailed in FIG. 2, a block flow diagram which outlines the major steps in continuous filament production. Ceramic powder feeds containing the various amounts of inorganic components detailed in the following numbered examples were prepared and introduced into a melt furnace, followed by melt conditioning and delivery to the bushing, followed by sizing and winding of the filaments. Diameters of samples were measured, and the filaments were tested for physical properties. Shrinkage characteristics for some samples were determined at 1800° F. 2100° F. and 2300° F.

Shrinkage Test

Shrinkage testing included the analysis of one gram of the tested fiber, ground and pressed into a bar. The linear shrinkage of the bars was measured with vernier calipers cold and then after heating at temperature. This method was confirmed by conducting the test on control K spun fibers and comparing the shrinkage of the K spun bar to the shrinkage of a blanket consisting of K spun fibers.

Tensile strength was tested at room temperature by a single filament measurement of a one inch gauge length section under strain. Young's modulus was determined from the tensile test data according to the equation ##EQU1##

EXAMPLES

As set forth in Table I, examples 1-30 represent samples wherein the concentration of one or more components falls outside the range of compositions defined by the present invention. In the "Composition" column of the Tables, the designation "RO" stands for metal oxides other than silica and alumina, and this column may alternatively contain designations of the derivation of the particular comparative fibers exemplified.

Examples 1-3 represent "S" glass and "E" glass compositions. The upper use temperature limits for these samples are much lower than those of the glass fibers of the present invention. Examples 4-5 (K Spun) represent conventional refractory ceramic fibers derived from kaolin which contain higher Al₂ O₃ percentages and lower MgO percentages than the fibers of the present invention. Examples 6-13 each contain MgO percentages lower than the fibers of the present invention. Examples 14-20 contain higher percentages of SiO₂, and lower percentages of Al₂ O₃ and MgO than the fibers of the present invention. Examples 21-22 contain lower Al₂ O₃ percentages than the fibers of the present invention. Examples 23-30 contain SiO₂, Al₂ O₃, and MgO within the ranges of the fibers of the present invention, but no TiO₂ is contained in any of examples 1-30. Examples 1-30 are comparative examples which demonstrate physical properties which are generally poorer than those of the fibers of the present invention. For example, the fibers described in examples 1-30 demonstrate much larger shrinkage percentages than the fibers of the present invention, except for examples 4 and 5 which are more comparable (although these fibers are discontinuous).

Examples 31-86 of Table I generally comprise all inventive components within the composition ranges defined by the present invention, except for those examples described as K Spun which are derived from kaolin and which were measured as control samples to monitor test accuracy for standard shrinkage properties, and examples 42, 54, and 55 which contain no TiO₂ but are included as additional comparative examples to illustrate the beneficial effect of TiO₂ (that is, "TiO_(x) ") in the fibers of the present invention.

Examples whose components fall within the inventive range of compositions described herein demonstrate generally improved physical properties and reduced shrinkage as compared to the comparative examples detailed above. In particular, examples of glass fibers of the present invention demonstrate increased tensile strength, increased Young's modulus and decreased shrinkage as compared to the comparative examples detailed above.

Examples 72-74, and 83-86 of the continuous filament glass fibers of the present invention exceed target properties with regard to improved strength, with values for tensile strength generally greater than 250 Ksi and Young's modulus generally greater than 12 Msi. Target properties for improved linear thermal shrinkage characteristics are demonstrated by examples 31-33, 37-39, 48-50, 51-53, 56-58, 62-65, 66-67, 68-70, 77-81, and 83-86 with values of less than 3% shrinkage at 2300° F. for 24 hours. These results may be compared to those of the comparative examples 4 and 5, which report standard K Spun refractory ceramic fibers with tensile strengths of 164-174 Ksi, Young's modulus values of 9.2-9.4 and a thermal shrinkage value of 3.4% at 2300° F. for 24 hours.

The beneficial effect of a narrow range of TiO₂ concentrations on shrinkage characteristics may be seen by comparing comparative example 24 and example 49. The base glass compositions for these two samples are nearly identical except for a 1.5 mole % addition of TiO₂ to example 49. The shrinkage of comparative example 24 was 10.9% at 2300° F. compared to only 1.8% for example 49. Example 44 shows that a lower level of TiO₂ is not as effective in reducing shrinkage (11.2% shrinkage) as the higher levels of examples 49 and 57 (1.6% shrinkage). Example 57 also illustrates the beneficial effect of the addition of 2% TiO₂ when compared to comparative example 54, without TiO₂, which demonstrates 18.8% shrinkage.

As reported in Table II, in Examples 87-91, the high temperature strength of continuous filament glass fibers (MT in FIGS. 3 and 4) made on an experimental multifilament bushing according to the invention were tested and Young's modulus determined at various temperatures, from 25° C. to 750° C. These were compared to fibers of commercial S glass comprising 68.6 mole % SiO₂, 15.6 mole % Al₂ O₃ and 15.8 mole % MgO (S2, COM) in examples 92-96, E glass (mb) produced on the multifilament bushing in examples 97-100, and S glass (S2 mb) produced on the multifilament bushing in examples 101-104. All fibers were tested at 3 inch gauge length.

The data for tensile strength tests and Youngs' modulus determinations are graphically represented in FIG. 3 and FIG. 4 respectively. The benefit of the inventive glass fiber compositions is demonstrated by the maintenance of tensile strength at high temperatures. As shown in FIG. 3, the slope of the strength curve of the inventive fiber decreases the least at high temperatures, and in fact, the inventive fiber has the highest strength at 750° C. of any of the fibers tested. The slopes of the strength curves of the S glass fibers were compared to a curve of the experimental data reported by Harris et al in U.S. Pat. No. 3,402,055 described above, and were found to coincide, thereby validating the test protocol.

As shown in FIG. 4, Youngs' modulus was demonstrated to be higher for the inventive glass fiber than for fibers of the comparative S and E glasses.

Thus, the objects of the invention are accomplished by the present invention, which is not limited to the specific embodiments described above, but which includes variations, modifications, and equivalent embodiments defined by the following claims.

                                      TABLE I                                      __________________________________________________________________________        Diam. Tensile                                                                              Mod                                                             EX.                                                                               (micron)                                                                             (KSI) (MSI) Shrinkage      Composition Mole %                         NO.                                                                               Mean                                                                              Std.                                                                              Mean                                                                              Std.                                                                              Mean                                                                              Std.                                                                              2300° F.                                                                     2100° F.                                                                     1800° F.                                                                     SiO.sub.2                                                                         Al.sub.2 O.sub.3                                                                   RO                                  __________________________________________________________________________     1  10.2                                                                              0.73                                                                              340.2                                                                             79.8                                                                              9.5                                                                               0.8                                                                               12.1 12.3 13.6 68.6                                                                              15.6                                                                               15.8 MgO (S-glass)                  2  16.0  106.0                                                                             15.3                                                                              10.3                                                                              0.8               57.4                                                                              9.1 33.5 (E-glass)                      3  11.2                                                                              0.83                                                                              231.8                                                                             43.2                                                                              8.8                                                                               0.3               57.4                                                                              9.1 33.5 (E-glass)                      4  8.6                                                                               3.49                                                                              164.2                                                                             59.1                                                                              9.2                                                                               2.3                                                                               3.4  2.1  0.9  66.7                                                                              30.0                                                                               3.0 (Kspun)                         5  13.4                                                                              4.28                                                                              173.7                                                                             71.9                                                                              9.4                                                                               2.6               66.7                                                                              30.0                                                                               3.0 (Kspun)                         6  11.5                                                                              0.87                                                                              147.3                                                                             49.9                                                                              5.9                                                                               1.6               86.3                                                                              10.5                                                                               3.2 CaO                             7  14.8                                                                              1.32                                                                              141.0                                                                             37.8                                                                              8.8                                                                               1.6     15.1 9.0  86.3                                                                              10.5                                                                               3.2 CaO                             8  10.7                                                                              3.95                                                                              134.7                                                                             39.4                                                                              8.2                                                                               1.5               86.3                                                                              10.5                                                                               3.2 CaO                             9  9.6                                                                               0.67                                                                              175.3                                                                             72.5                                                                              9.3                                                                               1.6               86.3                                                                              10.5                                                                               3.2 MgO                             10 9.3                                                                               0.89                                                                              201.7                                                                             70.3                                                                              10.4                                                                              2.6               86.3                                                                              10.5                                                                               3.2 MgO                             11 9.3                                                                               0.81                                                                              175.2                                                                             47.9                                                                              9.6                                                                               1.5                                                                               8.8       0.6  86.3                                                                              10.5                                                                               3.2 MgO                             12 10.2                                                                              0.29                                                                              193.4                                                                             64.8                                                                              9.8                                                                               0.8                                                                               15.3 17.0 2.0  86.3                                                                              10.5                                                                               3.2 BaO                             13 9.6                                                                               1.38                                                                              138.8                                                                             43.1                                                                              9.1                                                                               0.7     5.0       89.0                                                                              10.0                                                                               1.0 CaO                             14 7.5                                                                               0.64                                                                              161.6                                                                             46.4                                                                              9.9                                                                               3.3               90.5                                                                              5.2 4.3 ZrO.sub.2                       15 10.0                                                                              0.98                                                                              155.8                                                                             62.9                                                                              10.2                                                                              1.5               90.5                                                                              5.2 4.3 ZrO.sub.2                       16 12.1                                                                              0.89                                                                              92.9                                                                              30.3                                                                              8.1                                                                               1.6               90.5                                                                              5.2 4.3 TiO.sub.2                       17 13.7                                                                              0.51                                                                              120.7                                                                             42.9                                                                              9.0                                                                               0.9                                                                               5.4  3.6       90.5                                                                              5.2 4.3 TiO.sub.2                       18 15.0                                                                              0.88                                                                              102.7                                                                             57.8                                                                              8.1                                                                               1.4                                                                               8.2            90.5                                                                              5.2 4.3 ZrO.sub.2                       19 19.7                                                                              1.94                                                                              83.3                                                                              27.0                                                                              8.0                                                                               1.3               90.5                                                                              5.2 4.3 ZrO.sub.2                       20 11.7                                                                              0.75                                                                              114.8                                                                             40.3                                                                              9.5                                                                               1.7               90.5                                                                              5.2 4.3 TiO.sub.2                       21 10.4                                                                              1.59                                                                              193.1                                                                             62.7                                                                              10.6                                                                              2.4               84.9                                                                              7.5 7.6 ZrO.sub.2                       22 8.6                                                                               1.48                                                                              194.3                                                                             94.6                                                                              11.7                                                                              1.5               84.9                                                                              7.5 7.6 ZrO.sub.2                       23 10.5                                                                              0.23                                                                              229.3                                                                             57.3                                                                              11.2                                                                              1.2               78.1                                                                              13.9                                                                               8.0 MgO                             24 8.6                                                                               0.67                                                                              225.6                                                                             62.9                                                                              10.1                                                                              1.6                                                                               9.8  8.8  1.4  78.1                                                                              13.9                                                                               8.0 MgO                             25 16.2                                                                              1.71                                                                              183.9                                                                             40.2                                                                              10.2                                                                              1.1                                                                               10.9 10.2      78.1                                                                              13.9                                                                               8.0 MgO                             26 9.6                                                                               1.30                                                                              169.2                                                                             52.9                                                                              7.6                                                                               1.4                                                                               13.4 9.5  1.4  78.0                                                                              11.0                                                                               9 MgO, 2 ZrO.sub.2                  27 6.0                                                                               0.25                                                                              273.8                                                                             69.3                                                                              9.3                                                                               1.4               78.0                                                                              11.0                                                                               9 MgO, 2 ZrO.sub.2                  28 5.3                                                                               0.39                                                                              330.3                                                                             95.9                                                                              11.3                                                                              1.7                                                                               16.2 11.9 1.4  78.0                                                                              11.0                                                                               9 MgO, 2 ZrO.sub.2                  29 7.1                                                                               0.64                                                                              271.3                                                                             111.3                                                                             10.9                                                                              1.5               78.0                                                                              11.0                                                                               9 MgO, 2 ZrO.sub.2                  30 11.6                                                                              0.38                                                                              227.4                                                                             53.8                                                                              10.8                                                                              0.9               78.0                                                                              11.0                                                                               9 MgO, 2 ZrO.sub.2                  31 6.5                                                                               0.46                                                                              243.9                                                                             56.4                                                                              11.0                                                                              1.4                                                                               2.8  1.3       80.1                                                                              10.0                                                                               8.1 MgO, 1.8 TiO.sub.2              32 6.4                                                                               0.31                                                                              228.7                                                                             67.0                                                                              9.7                                                                               1.0               80.1                                                                              10.0                                                                               8.1 MgO, 1.8 TiO.sub.2              33 11.1                                                                              0.21                                                                              157.2                                                                             22.9                                                                              10.0                                                                              0.7               80.1                                                                              10.0                                                                               8.1 MgO, 1.8 TiO.sub.2              34                   3.1                   Kspun                               35 8.6                                                                               0.41                                                                              130.0                                                                             33.7                                                                              7.7                                                                               0.9                                                                               4.1            81.6                                                                              10.0                                                                               6.8 MgO, 1.6 TiO.sub.2              36                3.1                      Kspun                               37 6.4                                                                               0.41                                                                              143.9                                                                             47.7                                                                              8.4                                                                               1.1                                                                               2.2            78.0                                                                              10.0                                                                               10.5 MgO, 1.5 TiO.sub.2             38 5.8                                                                               0.01                                                                              178.9                                                                             57.1                                                                              9.4                                                                               0.4                      10.5 MgO, 1.5 TiO.sub.2             39 9.8                                                                               0.51                                                                              160.3                                                                             34.6                                                                              7.7                                                                               0.8               78.0                                                                              11.0                                                                               10.5 MgO, 1.5 TiO.sub.2             40                3.4                      Kspun                               41 9.3                                                                               0.30                                                                              178.3                                                                             36.0                                                                              9.1                                                                               0.7               78.0                                                                              10.0                                                                               10.5 MgO, 1.5 TiO.sub.2             42 8.4                                                                               0.78                                                                              161.0                                                                             51.0                                                                              8.0                                                                               1.3               78.0                                                                              11.0                                                                               11 Mg0                              43 7.1                                                                               0.22                                                                              270.3                                                                             101.4                                                                             9.3                                                                               0.7               78.0                                                                              12.0                                                                               9.0 MgO, 1.0 TiO.sub.2              44 13.1                                                                              0.23                                                                              137.4                                                                             83.7                                                                              8.8                                                                               0.4                                                                               11.2           78.0                                                                              12.0                                                                               9.0 MgO, 1.0 TiO.sub.2              45 9.0                                                                               0.20                                                                              209.9                                                                             94.3                                                                              9.2                                                                               0.6               78.0                                                                              12.0                                                                               9.0 MgO, 1.0 TiO.sub.2              46 7.7                                                                               0.15                                                                              205.9                                                                             65.1                                                                              9.1                                                                               0.5               78.0                                                                              12.0                                                                               9.0 MgO, 1.0 TiO.sub.2              47                   3.0                   Kspun                               48 5.6                                                                               0.18                                                                              245.3                                                                             52.7                                                                              10.2                                                                              0.8               78.0                                                                              12.3                                                                               8.2 MgO, 1.5 TiO.sub.2              49 7.0                                                                               0.13                                                                              231.5                                                                             34.9                                                                              10.3                                                                              0.5                                                                               1.8            78.0                                                                              12.3                                                                               8.2 MgO, 1.5 TiO.sub.2              50 10.9                                                                              0.18                                                                              183.3                                                                             23.0                                                                              10.0                                                                              0.3               78.0                                                                              12.3                                                                               8.2 MgO, 1.5 TiO.sub.2              51 15.1                                                                              0.15                                                                              204.3                                                                             34.4                                                                              11.7                                                                              0.4               81.0                                                                              10.0                                                                               7.5 MgO, 1.5 TiO.sub.2              52 9.8                                                                               0.11                                                                              204.6                                                                             36.1                                                                              12.0                                                                              0.4               81.0                                                                              10.0                                                                               7.5 MgO, 1.5 TiO.sub.2              53 21.8                                                                              0.62                                                                              181.5                                                                             35.4                                                                              10.5                                                                              0.4                                                                               1.1            81.0                                                                              10.0                                                                               7.5 MgO, 1.5 TiO.sub.2              54 6.2                                                                               0.30                                                                              194.0                                                                             78.0                                                                              8.7                                                                               1.0                                                                               18.8           78.0                                                                              11.0                                                                               11 MgO                              55 8.7                                                                               0.23                                                                              181.3                                                                             44.0                                                                              9.8                                                                               0.6               78.0                                                                              11.0                                                                               11 MgO                              56 9.1                                                                               0.36                                                                              176.8                                                                             36.0                                                                              9.5                                                                               0.8               78.0                                                                              10.0                                                                               10 MgO, 2 TiO.sub.2                 57 11.6                                                                              0.39                                                                              165.0                                                                             28.0                                                                              10.0                                                                              0.7                                                                               1.6            78.0                                                                              10.0                                                                               10 MgO, 2 TiO.sub.2                 58 8.4                                                                               0.47                                                                              151.0                                                                             52.0                                                                              8.8                                                                               1.1               78.0                                                                              10.0                                                                               10 MgO, 2 TiO.sub.2                 59 10.0                                                                              0.12                                                                              222.5                                                                             47.2                                                                              11.6                                                                              0.4               81.0                                                                              10.0                                                                               7.5 MgO, 1.5 TiO.sub.2              60 7.7                                                                               0.13                                                                              226.3                                                                             61.1                                                                              11.6                                                                              0.4               81.0                                                                              10.0                                                                               7.5 MgO, 1.5 TiO.sub.2              61                   2.4                   Kspun                               62 7.4                                                                               0.14                                                                              274.7                                                                             81.8                                                                              10.2                                                                              0.4               79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           63 9.1                                                                               0.12                                                                              214.9                                                                             87.4                                                                              10.4                                                                              0.3                                                                               2.2            79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           64 6.2                                                                               0.18                                                                              361.0                                                                             76.1                                                                              10.8                                                                              0.7               79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           65 13.2                                                                              0.16                                                                              179.4                                                                             65.4                                                                              11.8                                                                              0.4               79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           66 7.3                                                                               0.12                                                                              256.5                                                                             96.2                                                                              11.3                                                                              0.5                                                                               1.6            79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           67 9.6                                                                               0.13                                                                              212.9                                                                             68.1                                                                              11.6                                                                              0.4               79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           68 9.7                                                                               0.12                                                                              297.4                                                                             61.1                                                                              11.6                                                                              0.4               76.0                                                                              11.66                                                                              10.84 MgO, 1.5 TiO.sub.2            69 11.8                                                                              0.14                                                                              266.8                                                                             44.9                                                                              11.4                                                                              0.3                                                                               0.8            76.0                                                                              11.66                                                                              10.84 MgO, 1.5 TiO.sub.2            70 7.1                                                                               0.13                                                                              286.2                                                                             74.0                                                                              11.1                                                                              0.4               76.0                                                                              11.66                                                                              10.84 MgO, 1.5 TiO.sub.2            71                   2.5                   Kspun                               72 10.4                                                                              0.13                                                                              276.0                                                                             33.4                                                                              12.5                                                                              0.4               68.6                                                                              15.6                                                                               14.3 MgO, 1.5 TiO.sub.2             73 7.6                                                                               0.15                                                                              293.6                                                                             28.1                                                                              12.3                                                                              0.5                                                                               5.7            68.6                                                                              15.6                                                                               14.3 MgO, 1.5 TiO.sub.2             74 14.6                                                                              0.34                                                                              218.1                                                                             24.9                                                                              11.5                                                                              0.6               68.6                                                                              15.6                                                                               14.3 MgO, 1.5 TiO.sub.2             75                   10.8           68.6                                                                              15.6                                                                               15.3 MgO, 0.5 TiO.sub.2             76                   2.9                   Kspun                               77 6.1                                                                               0.26                                                                              320.0                                                                             36.0                                                                              11.8                                                                              1.2               76.0                                                                              11.66                                                                              10.84 MgO, 1.5 TiO.sub.2            78 9.4                                                                               0.44                                                                              270.6                                                                             46.2                                                                              10.9                                                                              0.9               76.0                                                                              11.66                                                                              10.84 MgO, 1.5 TiO.sub.2            79 14.5                                                                              0.65                                                                              213.0                                                                             36.9                                                                              10.5                                                                              0.9               76.0                                                                              11.66                                                                              10.84 MgO, 1.5 TiO.sub.2            80 4.1                                                                               0.21                                                                              281.0                                                                             42.0                                                                              10.2                                                                              1.0               76.0                                                                              11.66                                                                              10.84 MgO, 1.5 TiO.sub.2            81                   2.5            76.0                                                                              11.60                                                                              10.84 MgO, 1.5 TiO.sub.2            82                   3.3                   Kspun                               83                   1.7            79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           84 6.6                                                                               0.23                                                                              317.3                                                                             100.7                                                                             12.2                                                                              0.8               79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           85 10.8                                                                              0.59                                                                              248.7                                                                             87.9                                                                              13.3                                                                              1.5               79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           86 15.3                                                                              0.65                                                                              177.8                                                                             31.8                                                                              12.4                                                                              0.8               79.5                                                                              9.5 7.7 MgO, 1.5 TiO.sub.2, 1.8                                                    ZrO.sub.2                           __________________________________________________________________________

                                      TABLE II                                     __________________________________________________________________________     EX.                                                                               TEST DIAM. (microns)                                                                        TENSILE (KSI)                                                                          MOD (MSI)                                                                              COMPOSITION MOLE %                             NO.                                                                               TEMP °C.                                                                     MEAN                                                                               STD.                                                                               MEAN                                                                               STD.                                                                               MEAN                                                                               STD.                                                                               SIO.sub.2                                                                         AL.sub.2 O.sub.3                                                                   RO                                      __________________________________________________________________________     87 25.0 15.9                                                                               0.69                                                                               184.8                                                                              27.6                                                                               13.7                                                                               1.2 67.5                                                                              15.3                                                                               15.5 MgO, 1.5 TiO.sub.2                 88 25.0 16.0                                                                               0.54                                                                               190.2                                                                              35.5                                                                               13.6                                                                               0.9 67.5                                                                              15.3                                                                               15.5 MgO, 1.5 TiO.sub.2                 89 260.0                                                                               15.9                                                                               0.43                                                                               181.9                                                                              44.4                                                                               13.4                                                                               0.7 67.5                                                                              15.3                                                                               15.5 MgO, 1.5 TiO.sub.2                 90 500.0                                                                               15.9                                                                               0.53                                                                               177.3                                                                              30.4                                                                               13.5                                                                               1.0 67.5                                                                              15.3                                                                               15.5 MgO, 1.5 TiO.sub.2                 91 750.0                                                                               16.0                                                                               0.50                                                                               121.7                                                                              23.5                                                                               11.2                                                                               0.8 67.5                                                                              15.3                                                                               15.5 MgO, 1.5 TiO.sub.2                 92 25.0 9.6 1.10                                                                               393.4                                                                              70.6                                                                               12.5                                                                               0.6 (S2 COM)                                       93 25.0 9.2 1.06                                                                               451.7                                                                              91.5                                                                               13.6                                                                               0.6 (S2 COM)                                       94 260.0                                                                               9.3 0.92                                                                               332.6                                                                              60.7                                                                               12.4                                                                               0.8 (S2 COM)                                       95 500.0                                                                               9.7 0.59                                                                               333.5                                                                              56.6                                                                               12.1                                                                               0.5 (S2 COM)                                       96 750.0                                                                               9.7 0.97                                                                               159.0                                                                              17.4                                                                               10.1                                                                               0.6 (S2 COM)                                       97 25.0 6.5 0.56                                                                               211.9                                                                              49.2                                                                               10.6                                                                               0.7 E Glass (mb)                                   98 250.0                                                                               6.8 0.44                                                                               223.2                                                                              68.0                                                                               10.2                                                                               0.5 E Glass (mb)                                   99 500.0                                                                               6.7 0.40                                                                               197.6                                                                              28.2                                                                               9.2 0.8 E Glass (mb)                                   100                                                                               600.0                                                                               6.8 0.49                                                                               152.4                                                                              25.0                                                                               8.4 0.7 E Glass (mb)                                   101                                                                               25.0 8.2 1.39                                                                               366.5                                                                              46.8                                                                               12.9                                                                               0.6 S2 mb                                          102                                                                               250.0                                                                               8.2 0.72                                                                               294.7                                                                              56.5                                                                               12.7                                                                               0.5 S2 mb                                          103                                                                               500.0                                                                               8.0 1.02                                                                               299.7                                                                              60.6                                                                               12.0                                                                               0.7 S2 mb                                          104                                                                               750.0                                                                               8.2 1.20                                                                               141.8                                                                              40.1                                                                               9.6 0.9 S2 mb                                          __________________________________________________________________________ 

We claim:
 1. A friction pad comprising a reinforced organic matrix material, wherein the matrix is reinforced with at least one reinforcement material, said at least one reinforcement material including high temperature stable glass fibers consisting essentially ofi) about 67.5 to about 85 mole percent SiO₂, ii) about 9.5 to about 20 mole percent Al₂ O₃, iii) about 5 to about 15.5 mole percent MgO, iv) about 0.5 to about 5 mole percent TiO_(x), wherein 0≦x≦2, and v) 0 to about 5 mole percent ZrO₂.
 2. The friction pad of claim 1, wherein TiO_(x) is present in the amount of about 1 to about 2 mole percent.
 3. The friction pad of claim 1, wherein the high temperature stable glass fibers are substantially uniformly sized chopped fibers.
 4. The friction pad of claim 3, wherein the high temperature stable glass fibers are a mixture of selected sizes of substantially uniformly sized chopped fibers.
 5. The friction pad of claim 3, wherein the high temperature stable glass fibers have a length in the range of about 1/16 inches to about 3/4 inches.
 6. The friction pad of claim 3, wherein the high temperature stable glass fibers have a length in the range of about 1/16 inches to about 1/4 inches.
 7. The friction pad of claim 1, wherein the matrix material comprises a phenolic binder.
 8. The friction pad of claim 1, wherein the loading level of the high temperature stable glass fiber in the matrix is about 1% by weight to about 50% by weight of the total weight of reinforced matrix material.
 9. The friction pad of claim 8, wherein the loading level of the high temperature stable glass fiber in the matrix is about 2% by weight to about 30% by weight of the total weight of reinforced matrix material.
 10. The friction pad of claim 9, wherein the loading level of the high temperature stable glass fiber in the matrix is about 5% by weight to about 20% by weight of the total weight of reinforced matrix material.
 11. The friction pad of claim 1, wherein at least a second reinforcement material includes E glass.
 12. The friction pad of claim 1, wherein the high temperature stable glass fibers exhibit a tensile strength greater than about 250 Ksi.
 13. The friction pad of claim 1, wherein the high temperature stable glass fibers exhibit a Young's modulus greater than about 12 Msi.
 14. The friction pad of claim 1, wherein the high temperature stable glass fibers have an average diameter of about 5 to about 25 microns.
 15. The friction pad of claim 1, wherein the high temperature stable glass fibers comprise about 68 to about 82 mole percent SiO₂, about 10 to about 18 mole percent Al₂ O₃, about 6 to about 14 mole percent MgO, about 1 to about 2 mole percent TiO_(x), and 0 to about 3 mole percent ZrO2.
 16. The friction pad of claim 1, wherein the high temperature stable glass fibers comprise about 72 to about 80 mole percent SiO₂, about 10 to about 16 mole percent Al₂ O₃, about 7 to about 14 mole percent MgO, about 1.25 to about 1.5 mole percent TiO_(x), and about 0 to about 2 mole percent ZrO₂.
 17. The friction pad of claim 1, wherein the high temperature stable glass fibers of claim 1 wherein ZrO₂ is present in an amount effective to achieve a mean tensile strength of at least 175 Ksi.
 18. The friction pad of claim 1, comprising a disc brake pad.
 19. The friction pad of claim 18, comprising an automotive disc brake pad.
 20. The friction pad of claim 19, comprising a light truck disc brake pad.
 21. The friction pad of claim 1, comprising a clutch friction pad.
 22. The friction pad of claim 1, comprising a brake shoe for a drum brake.
 23. The friction pad of claim 1, comprising a heavy duty truck brake block. 